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Information presented herein pertains to proprietary products.

External Post-Tensioning for Full-Depth Precast Deck Panels

AccelBridge A B

Prepared for 2012 Virginia Concrete Conference

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Today’s Presentation

• Full-Depth Precast Decks - Current Industry Practice • The AccelBridge Systems - Construction / Engineering

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The Search for an Ideal ABC System

SPMTs

Slide-In / Float-In

Segmental Full-Depth Precast Decks

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Full-Depth Precast Decks

Full depth precast deck system advantages: • Uses standard girder shapes • Doesn’t require special equipment • Relatively simple technology

I-287 Cross Westchester

Expressway, New York • Value engineering • A+B project • Minimize field labor • 300,000 sq ft of precast deck

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Full-Depth Precast Panels: Current Practice

Shim pack to support panel

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Full-Depth Precast Panels: Current Practice

•Duct Coupling •Durability Concerns

•Extensive Duct Work •Panel Alignment

•CIP joint field works •Durability concerns

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Attempts to Eliminate Deck PT Anchorage Tube Connection

• Unreliable grouted joint interfaces

Full-Depth Precast Panels:

UHPC (Ultra-High

Performance Concrete) • Very expensive • Demanding on

workmanship

No compression across deck joints = Durability Concerns

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Full-Depth Precast Panels: AccelBridge

Simplicity Durability Speed Cost Current system

No PT ducts in panels 400+ pcs

No grouted joints 20 joints

No duct couplers 400+ couplers

Save materials 12,000 lbs PT or two girder lines

(Comparison from example bridge: 43 ft wide, 105 ft – 105 ft span)

Goal Achieved: Maintaining compression across deck joints without PT in the panels

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The AccelBridge Systems

AccelBridge is a patented technology consisting of four systems: • AccelNP: Steel girders - no post-tensioning

• AccelPB: Concrete girders with tensioned rods at pier

• AccelPG: Concrete girders with post-tensioning in the girders

• AccelPD: Concrete tub girders with external post-tensioning Simple construction with proven technologies.

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AccelPG System

• No internal deck post-tensioning • Deck compression is provided by PT internal to precast concrete girders

(no coupling, less duct work, more efficient girder) • System is very similar to typical post-tensioned precast girders, but with an

innovative construction sequence

PT in girder

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Principles

Dual function of girder post-tensioning: • Longitudinal component provides deck compression • Vertical component (deviation force) helps the girder resist load

-Very effective use of PT, saving girder materials

AccelPG System

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• Construct substructures • Erect girders

AccelPG System - Construction

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Leave a small gap between girders at pier

AccelPG System - Construction

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Erect all deck panels

AccelPG System - Construction

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Grout Pockets in End Panels

AccelPG System - Construction

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Stress girder post-tensioning tendons

AccelPG System - Construction

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• Grout haunch and shear connectors for all remaining panels.

• Finish diaphragms at abutments and pier

AccelPG System - Construction

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AccelPG System - Advantages

AccelBridge • 4 girder lines • 8 duct couplers • 8 tendons (11,340 lbs)

Conventional Full Depth Precast • 6 girder lines • 360 duct couplers • 18 tendons (11,340 lbs)

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• Precast deck with steel girders • Precompression of precast deck is provided by jacking against steel girders • Best with NSBA simple for dead load and continuous for live load detail • Can be used for deck replacement reusing existing girders

AccelNP System

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AccelNP System

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Simple span for dead load, continuous for live load layout: ►Jacking helps the girder resist load

AccelNP System

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AccelNP System – Pier Connection

Top Flange Splice for Dead Load

Bottom Flange Grouted Splice for Live Load (Modified NSBA)

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AccelNP System – Construction

Erect Girders

Top Flange Splices

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AccelNP System – Construction Place Deck Panels

Space to Place Jacks

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Grout End Panel

Grout End Panel

Perform Jacking Operations

AccelNP System – Construction

Jacks

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AccelNP System – Construction

Place CIP Pour Backs prior to Removing Jacks

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AccelNP System – Construction

Remove Jacks and Complete Closure Pour

Grout all panels

Bottom Flange Grouted Splice at Pier

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AccelNP System

Alternative Jacking method • Use jacking frame welded to steel girder • Eliminate closure pour

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AccelNP System – Advantages

AccelBridge • No PT (maintains same

deck compression) • No duct couplers

Conventional Full Depth Precast • 22 x 4-0.6” PT (13,860 lbs) • 440 duct couplers

Also applicable to deck replacement of existing bridges.

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• Typical precast prestressed concrete girders • Two or more spans • Deck compression provided by tensioning rods at pier

AccelPB System

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AccelPB System

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Erect girders

AccelPB System - Construction

PT Bars Details at Piers

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AccelPB System - Construction

Place Deck Panels

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Grout End Panels

AccelPB System - Construction

Grout End Panels

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Stress PT Bars at Piers

AccelPB System - Construction

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Grout Haunch and Shear Connectors for All Remaining Panels.

AccelPB System - Construction

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AccelPB System - Advantages

AccelBridge • 12 x1 ¾” dia threaded rod

(1150 lbs) • No duct couplers • Girder strand savings

Conventional Full Depth Precast • 18 x 4-0.6” PT Tendons (11340 lbs) • 360 duct couplers

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Deck PT anchored at the end segment provide the compression force

Deck PTs exit end segment and become external

Deviation force produced by deck PT assists the girder in resisting load

• Precast deck with external post-tensioning inside Precast Tub girders • An economical alternate to segmental box girder • Combines the best from two proven technologies:

– Concrete segmental bridges with external post-tensioning – Full depth precast deck

AccelPD System

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AccelPD System

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AccelPD System - Construction

Erect Girders

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AccelPD System - Construction

Install PT and Place End Panels

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AccelPD System - Construction

• Install All Deck Panels

• Stress PT • Grout all pockets

and haunches

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AccelPD System - Advantages

Segmental • Expensive formwork • Expensive erection

system • Special construction

experience required

AccelPD

• No expensive formwork • Conventional erection • No special construction

experience required

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AccelBridge Applications

Spans Construction Girders

Single Multi New Deck Replace Conc. Steel

AccelPD

AccelPG

AccelPB

AccelNP

The AccelBridge Systems are extremely versatile: • U- and I-girder shapes • Steel and concrete girders • New construction and deck replacements • Single and multiple spans

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The match cast method, popular in segmental construction, is an ideal solution for full depth precast deck

• Simplified long-line match casting method • “Flat” casting • Maximum deck curvature only results in <2mm gap at joints • Segmental construction typically allows 3mm epoxy joints.

• MODOT’s very successful example of Nemo Bridge (construction by Columbia Curb & Gutter)

Match-Cast Joints

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Step 1 - Cast every other segment with bulkheads

Step 2 – Match cast the remaining segments

Match-Cast Joints

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• Need to consider camber due to stressing the deck (after deck placement)

Engineering Topics

• Girder Stress Distribution

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The deck is very thin in the vertical direction -- its stability must be ensured under such a large compression force.

Therefore: Checking deck stability is one of the most important tasks in

the design of the AccelBridge systems. Theory: • Gravity force provides the stabilizing force – buckling of the deck has to

overcome the gravity force first • The deck stability shall consider bridge profile geometry and

construction tolerance.

Engineering Topics: Deck Stability

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Potential destabilizing effects from bridge vertical profiles:

Engineering Topics: Deck Stability

Potential destabilizing effects from construction tolerance:

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Level 1 – Point B unloads Level 2 – Point C unloads

Engineering Topics: Deck Stability

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Engineering Evaluation Results: Typically, a safety factor of two against buckling can be readily achieved. However, hold-down devices can provide additional safety margin:

Engineering Topics: Deck Stability

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Typical Deck Internal PT • Joints and couplers are always

the “weak links” • Chloride can penetrate through

joints and couplers

AccelBridge • PT ducts are away from deck and are

well protected (AccelPG and AccelPD) • No PT ducts (AccelNP and AccelPB)

The AccelBridge Advantage: Durability

Extremely Durable Deck System • Precast and cured in shop environment • Can provide zero tension in the deck • No weak spots (no PT, no coupler in the deck)

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• All four AccelBridge systems can accommodate future deck replacement

• Future deck replacement for AccelNP, AccelPB and AccelPD can follow the same sequence as for their original construction

• Future deck replacement for AccelPG uses a jacking method similar to AccelNP

The AccelBridge Advantage: Deck Replacement

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The AccelBridge Advantage

No Complicated Equip.

Deck Panels Simplified

Field Labor Minimized

Durability Enhanced

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AccelBridge Improves constructability; less field labor, less risk. AccelBridge Offers an extremely durable deck system. AccelBridge Saves money -- both upfront and over the bridge lifecycle.

The AccelBridge Advantage

AccelBridge = ABC Made Simple.

A B ABC Made Simple.

Information presented herein pertains to proprietary products.

AccelBridge A B Put AccelBridge to work for you. Contact us at: Eddie He, PE, SE, PhD, LEED AP Phone: 312.952.3071 E-mail: info@accelbridge.com